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Old 06-27-2016, 02:57 PM   #41
Bus Crazy
 
Join Date: Jun 2016
Location: Orange County, CA
Posts: 1,356
Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
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Quote:
Originally Posted by PNW_Steve View Post
Detroit 671N info?

Hey Everyone,

Thank you for all of the discussion. I love to sit back and listen to folks who are more knowledgeable than I am on a subject discuss it. Educational and entertaining

I have put many miles on DD 2 strokes and they hold a special place for me. However, I have never even seen a "pancake" 671.

I have been searching for details regarding the difference between the regular 671 and the "pancake". I would guess from DD practices that parts commonality would be good. Just guessing though.

How about parts availability?

Is it likely that I may find a Crown with a factory 671T or TA?

Lastly.... I am eyeballing a couple of Crown's that are equipped with 5 speed manual's. Neither seller can identify what transmission it is. I am guessing that it is the Spicer MD 5 speed??? What can you all tell me about this trans? How about swapping in a 7 or 9 speed?
The major difference between pancake and upright Detroits (and presumably also Cummins) is the oil pan and oil pump. With the right parts it is theoretically possible to convert an upright Detroit to a pancake for a Crown or Gillig - however, finding those parts these days may be impossible. It's easier to just find a bus with the right engine.

Crown used both non-turbo and turbo versions of the pancake 6-71 in their Twinkies. The non-turbo has about 215 HP, and the turbo has 270 HP. With a 10-speed transmission even a non-turbo Detroit Crown is reasonably quick, and a 6-71T with a Roadranger 10-speed is a brisk performer. My friend's 40-foot Crown tandem with a 6-71T and RT-910 Roadranger climbed Tehachapi in 9th gear, and his bus is heavier than 35-foot Crowns. There's at least as many turbo Crowns out there as non-turbos, so if you want one just be patient - school districts in CA are beginning to sell off their non-CARB Crowns now.

Remember, no two Crowns are alike. Every one was built to order, and as long as Crown could get the parts the customer wanted they would build it. Some thrifty school districts bought low-spec buses, especially if they are in non-mountainous areas, but some districts speced their Crowns with all the bells and whistles - sanders, extra heaters, Jake brakes or retarders, A/C or power vents, tinted windows, highway gearing, extra baggage compartments, etc etc. For example, Eastern Sierra's Crowns had almost every available option, but they were covering several hundred miles a day. Often the buses from mountain districts are better speced.

John

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Old 06-27-2016, 03:12 PM   #42
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Quote:
Originally Posted by PNW_Steve View Post
Detroit 671N info?

Hey Everyone,

Thank you for all of the discussion. I love to sit back and listen to folks who are more knowledgeable than I am on a subject discuss it. Educational and entertaining

I have put many miles on DD 2 strokes and they hold a special place for me. However, I have never even seen a "pancake" 671.

I have been searching for details regarding the difference between the regular 671 and the "pancake". I would guess from DD practices that parts commonality would be good. Just guessing though.

How about parts availability?

Is it likely that I may find a Crown with a factory 671T or TA?

Lastly.... I am eyeballing a couple of Crown's that are equipped with 5 speed manual's. Neither seller can identify what transmission it is. I am guessing that it is the Spicer MD 5 speed??? What can you all tell me about this trans? How about swapping in a 7 or 9 speed?
From what I can learn via Google, there appears to be little difference in a 6-71 in a traditional installation versus a 'pancake' installation. It sounds like the engine block was very versatile for a variety of applications including marine use. For that reason I would guess there's probably a large cache of spare parts out there.

As for finding a Crown with a 671T, I can't find any references BUT if you are willing to look at transit buses it appears these were used in city buses made by Flxible and used in markets like Spokane and Portland. Happy hunting!
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Old 06-27-2016, 03:14 PM   #43
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John beat me to the punch and with better info!
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Old 06-27-2016, 03:22 PM   #44
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Quote:
Originally Posted by Iceni John View Post
The major difference between pancake and upright Detroits (and presumably also Cummins) is the oil pan and oil pump. With the right parts it is theoretically possible to convert an upright Detroit to a pancake for a Crown or Gillig - however, finding those parts these days may be impossible. It's easier to just find a bus with the right engine.

Crown used both non-turbo and turbo versions of the pancake 6-71 in their Twinkies. The non-turbo has about 215 HP, and the turbo has 270 HP. With a 10-speed transmission even a non-turbo Detroit Crown is reasonably quick, and a 6-71T with a Roadranger 10-speed is a brisk performer. My friend's 40-foot Crown tandem with a 6-71T and RT-910 Roadranger climbed Tehachapi in 9th gear, and his bus is heavier than 35-foot Crowns. There's at least as many turbo Crowns out there as non-turbos, so if you want one just be patient - school districts in CA are beginning to sell off their non-CARB Crowns now.

Remember, no two Crowns are alike. Every one was built to order, and as long as Crown could get the parts the customer wanted they would build it. Some thrifty school districts bought low-spec buses, especially if they are in non-mountainous areas, but some districts speced their Crowns with all the bells and whistles - sanders, extra heaters, Jake brakes or retarders, A/C or power vents, tinted windows, highway gearing, extra baggage compartments, etc etc. For example, Eastern Sierra's Crowns had almost every available option, but they were covering several hundred miles a day. Often the buses from mountain districts are better speced.

John

Hey John,

Thanks for the info!!

That eases my mind. If, for example, I lost a rotor seal and had a runaway then I could find a good running 671 and move the oil pan etc from the dead motor. Not a lot of unique pieces.

As far as the CA school districts go, I have been told that the majority of the Crowns have already been or are about to be crushed.

Any thoughts regarding swapping a 9 or 10 speed for a factory 5 speed?

Thanks again.
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Old 06-27-2016, 03:36 PM   #45
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Goes without saying, but the 855 big cam would be awesome.
Crowns were some amazing school buses.
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Old 06-27-2016, 04:54 PM   #46
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columbus ohio had a bunch of flxibles and were quickly retired due to many service issues... A/C, electrical and frame cracks were some of the big reasons they were retired before normal criteria and were replaced with mainly Gillig's...

-Christopher
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Old 06-27-2016, 06:06 PM   #47
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I guess Flxibles were too, well, flexible? Lol
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Old 06-27-2016, 10:35 PM   #48
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Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
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Originally Posted by EastCoastCB View Post
Goes without saying, but the 855 big cam would be awesome.
Crowns were some amazing school buses.
My friend's Gillig tandem has a big-cam Cummins 855 set at 290 HP, and it moves! He jokingly says it will do 65 MPH up whatever hill you point it at, and that's not far off the truth. One day we took it up to Wrightwood ski resort, and we were having to slow for the curves going uphill! That's what 14 liters and over 1,000 lb/ft of torque does. Then on the way back I don't think he touched the brakes at all, the three-stage Jake holding our speed all the way down. What a beast! If you want the ultimate Crown, get one with a Cummins 855 and turn it up to 400 HP - with the right gearing you'll have a 90+ MPH bus! The articulated Crown/Ikarus 286 transit buses that were used in Portland and elsewhere had 350 HP pancake Cummins engines - apparently they were quite strong performers.

Because Crowns (and Gilligs) were built with standard Class-8 truck parts such as drivetrains and brakes, they can be rebuilt or upgraded just like any heavy truck can. Only your imagination and wallet limit what's possible.

John
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Old 06-28-2016, 01:50 AM   #49
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Quote:
Originally Posted by PNW_Steve View Post
Hey John,

Thanks for the info!!

That eases my mind. If, for example, I lost a rotor seal and had a runaway then I could find a good running 671 and move the oil pan etc from the dead motor. Not a lot of unique pieces.

As far as the CA school districts go, I have been told that the majority of the Crowns have already been or are about to be crushed.

Any thoughts regarding swapping a 9 or 10 speed for a factory 5 speed?

Thanks again.
\

Swapping in a Road Ranger multi-range transmission in place of the 5-speed is a pretty straight forward swap. Both use the same single shaft gear shift so the hardest part of the swap is just a matter of sliding the shifter into the top of the transmission. You may (most probably) have to have the driveline shortened as the multi-range transmissions tend to be longer than the 5-speeds.

Our church has a 1986 Crown with a 6-71TAC. You have to remember not to floor it from a stand still but ease into the throttle. If you mash the go pedal on the start you throw up a smoke screen that would impress most of those idiots that are always "blowin' coal". But if you ease into it and let the turbo spool up it won't smoke at all. Gearing limits the top speed but it will cruise all day up and down hills at 70 MPH. I can't remember if the HP is set at 250 or 280. I tend to think it is the lower number since it has an MT640 and not an HT740 transmission.
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Old 06-28-2016, 01:11 PM   #50
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Anyone in the Everett, WA area?

I hear rumor of a Crown tandem parked/abandoned on the flats between Everett & Marysville.

Anyone seen it?
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Old 06-28-2016, 07:53 PM   #51
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Originally Posted by PNW_Steve View Post
Anyone in the Everett, WA area?

I hear rumor of a Crown tandem parked/abandoned on the flats between Everett & Marysville.

Anyone seen it?
I just passed by one sitting in a lot in Billings, MT... Not a Crown I don't think but it was a tandem axle so who else made a WestCoastER style bus? It looked pretty rough and parted out but just to have that frame and axle set would be nice.
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Old 06-28-2016, 10:19 PM   #52
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Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
Quote:
Originally Posted by jake_blue View Post
I just passed by one sitting in a lot in Billings, MT... Not a Crown I don't think but it was a tandem axle so who else made a WestCoastER style bus? It looked pretty rough and parted out but just to have that frame and axle set would be nice.
Crown and Gillig made md-engine 40-foot tandem school buses (both axles driven, with a lockable inter-axle differential for snowy/icy conditions); I was told that Gillig also made some pusher tandem school buses, but I've never seen a picture of one. Crown also made high-floor 3-axle tour buses, such as the Atomics built for the AEC to ferry workers to nuclear sites in Idaho and elsewhere, that had 8V71 Detroits and tag axles: only one axle was driven. Thomas WestCoastERs were made in 3-axle versions to compete with Crown and Gillig, but I don't know if they had single or double axle drive. I saw a brochure picture once of a Blue Bird All American pusher 3-axle demonstrator, but was it the only one ever made? 3-axle school buses were only for the West Coast markets, especially the difficult mountain or desert school districts.

The first ever three-axle Crown school bus, a 1955, still exists - it belongs to a friend of mine. It originally had a Hall-Scott gasoline engine, but was later repowered with a Cummins 220 (which unfortunately seized while being driven back from OR to CA). What makes it interesting is its rear axles arrangement - the drive axle is the rearmost one, and it looks like something from a military truck with its top-loader design of differential. The other rear axle looks like a front axle and is ahead of the drive axle, and its wheels were driven by some large V-belts or bands from the drive axle's wheels. Needless to say, these drive belts are now long gone. I hope that at some point this historically important bus will be restored to its former glory, but there's lots of hard work ahead to get there.

John
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Old 06-29-2016, 08:11 AM   #53
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Any idea how I share pics here?
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Old 06-29-2016, 08:43 AM   #54
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I was mistaken, it's not tandem drive axles, the rear is only a tag axle... But it's got Blue Bird mudflaps! Must be a Wanderlodge.
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Old 06-29-2016, 06:09 PM   #55
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Issaquah school district had a bunch of Gillig 10-wheeler RE buses in the mid-'70's. It has been so long ago I don't remember if they were stick or automatic. They most likely had the Cat 1160, the forerunner of the 3208. Since Issaquah has a lot of hills I would imagine both axles were driven.

The belt drive you describe sounds like the same sort of poor mans differential interlock Greyhound used on their Scenicruisers. All they were was a very large cogged fan belt that was put between the duals before the outside tire was put on the bus. There was a disc that went between the duals on which the belt rode. It didn't work all that well but it was enough to keep the Scenicruisers from being stuck all the time.

Longview school district had two Thomas West-Coast-ER 10-wheelers with Cat 3208T with Allisons. Only the rear axle was driven, the middle axle was just along for the ride.
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Old 06-29-2016, 07:09 PM   #56
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That actually gets me to wondering if there is any value to wear a drive axle is position in a 3-axle vehicle. I am used to seeing on contemporary coaches a tag axle in the back which means the drive axle is in the middle but I think there are earlier buses that predate me obviously which have a tag axle in the middle and the drive is in the rear and I just don't know how those arrangements very one from another in terms of performance or ride quality.
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Old 06-29-2016, 07:20 PM   #57
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Quote:
Originally Posted by jake_blue View Post
I was mistaken, it's not tandem drive axles, the rear is only a tag axle... But it's got Blue Bird mudflaps! Must be a Wanderlodge.
The Crown tandem I looked at a month or so ago had both axles as drivers.
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Old 06-30-2016, 12:13 AM   #58
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Rated Cap: 37,400 lbs GVWR
Quote:
Originally Posted by jake_blue View Post
That actually gets me to wondering if there is any value to wear a drive axle is position in a 3-axle vehicle. I am used to seeing on contemporary coaches a tag axle in the back which means the drive axle is in the middle but I think there are earlier buses that predate me obviously which have a tag axle in the middle and the drive is in the rear and I just don't know how those arrangements very one from another in terms of performance or ride quality.
Early model Eagles had their tag axle ahead of the drive axle, and they were known for a sometimes bouncy ride in the front. Mind you, some of that may have been because of their Torsilastic suspension.

John
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Old 06-30-2016, 01:20 AM   #59
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Originally Posted by jake_blue View Post
That actually gets me to wondering if there is any value to wear a drive axle is position in a 3-axle vehicle. I am used to seeing on contemporary coaches a tag axle in the back which means the drive axle is in the middle but I think there are earlier buses that predate me obviously which have a tag axle in the middle and the drive is in the rear and I just don't know how those arrangements very one from another in terms of performance or ride quality.
The pivot point for going around a corner is the center of the drive axle. On buses with a bogey axle the pivot point is the rear axle. On buses with a tag axle the pivot point is the middle axle. When it comes time to get around a corner that extra five feet of wheelbase makes a big difference on how sharp you can cut the corner.

On Crown 10-wheelers, the pivot point was not that much different than on a regular two axle bus. The distance from the rear bumper to the center of the rear axle is the same as a two axle bus. The distance between the front axle and the second axle is the same as a two axle bus. You needed a little more space to get around a corner with a 10-wheeler because you have to slide everything around. But it would turn just about as sharp as a two axle and better than almost any RE bus.
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Old 06-30-2016, 06:15 AM   #60
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Quote:
Originally Posted by Iceni John View Post
Early model Eagles had their tag axle ahead of the drive axle, and they were known for a sometimes bouncy ride in the front. Mind you, some of that may have been because of their Torsilastic suspension.

John
That's what I recall hearing but couldn't understand why that would be due to the tag axle position. I'd give more credence to the suspension system.

I know turning radius can be affected by tandems and tag axles and contemporary coaches have countersteering tag axles to prevent the 'subordinate' axle from scrubbing it's tires in the sideways motion of parking lot and corner turns. In trucking when you have three and four or more axles on a trailer you also have lift control or else you can't turn the trailer without dragging some of the tires sideways, causing wear and tear on the tires and burdening your engine trying to overcome the lateral drag. I know the problem isn't as pronounced in a tag axle or tandem coach configuration but I figured it's still a minor factor.

I appreciate the feedback and insight.
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